Help the other person left and I only got 30 mins to finish

1/8 or 12.5%

Step-by-step explanation:

The amount of yellow is 1 out of 8 pieces. 1/8 in percent form is 12.5%

12.5%

Step-by-step explanation:

Out of 8 sections, 1 is yellow

1/8 × 100 = 12.5%

-cos(2A)

Step-by-step explanation:

We know that (a+b) (a-b) = a^2-b^2

So it means we can simplify to sin^2(A)-cos^2(A) and we know cos^2(A) - sin^2(A) = cos(2A) but we will just multiply by -1 and we get - cos(2A)